<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        /* 选择器嵌套的越深权重就越高 */
        .one{
            color:red;
        }
        body>div>p.one{
            color:green;
        }
    </style>
</head>
<body>
    <div>
        <p id="one" class="one">hello world</p>
    </div>
</body>
</html>